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KMID : 1159320080100020147
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Korean Journal of Vision Science
2008 Volume.10 No. 2 p.147 ~ p.155
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Comparison of Repeatability of Heterophoria Measurement Techniques by Gradient AC/A ratio
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Jeon In-Chul
Mah Ki-Choong
Jang Man-Ho
Doo Ha-Young
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Abstract
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Purpose: To compare the repeatability of heterophoria testing with free space and mechanical space. The subjects were 67 healthy men and women between the age of 20 to 34 (mean 26.11±2.56) years old.
Methods: Refractive error in subjects was measured using the Auto-refractormeter (KR-7100P, Topcon Co.) and subjective refraction. Binocular vision function was measured using the Phoropter (Shin-Nippon BR-7), Chart project (Topcon ACP-7), Trial Frame (FM580), Lens Holder Kit (Gulden Ophthalmics co.), Loose Prism, MIM Card (Bernell co.), Prism Bar (Gulden Ophthalmics co.).
Results: The deviation was measured for viewing distance of 5m and 0.40m using both phoropter and trial frame. The mean horizontal deviations in phoropter was VG (distance) -0.78±2.14△, VG (near) -2.63±4.64△, MR (distance) -0.35±1.85△, MR (near) -1.69±4.80△, MT (distance) -0.40±1.81△, MT (near) -1.78±4.52△. The mean horizontal deviations in trial frame was VG (distance) -0.36±1.70△, VG (near) -1.43±4.00△, MR (distance) -0.08±1.54△, MR (near) -1.07±4.15△, MT (distance) -0.13±1.75△, MT (near) -1.24±4.46△. Mean values of gradient AC/A ratio with mechanical space measured using the VG, MR and MT procedures were 3.32±0.81△, 3.07±0.61△and 2.74±0.29△. AC/A ratio with free space measured using the VG, MR and MT procedures were 3.27±0.7△, 3.11±0.64△and 2.57±0.26△.
Conslusions: The measurement of phoria and AC/A ratio vary a little according to the phoria testing method, and amount of phoria measured in free space and limited space vary according to the procedures, but it is considered not to make a significant difference clinically. I think that ratios obtained using the MT showed the best repeatability, whereas the poorest repeatability was found with the VG.
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KEYWORD
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Binocular vision, Heterophoria, AC/A raito, Phoria test
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